Automatic control means for retarders



Nov. 1, 1966 R. J. BERTI 3,283,146

AUTOMATIC CONTROL MEANS FOR RETARDERS Filed Jan. 6. 1954 e Sheets-Sheet1 Fial INVENTOR ROLAND d. 5597/ ATTORNEYS 6 Sheets-Sheet 2 R. J. BERT] 6J47 k l AUTOMATIC CONTROL MEANS FOR RETARDERS INVENTOR POL/1ND r/. 55977 ATTORNEYS Nov. 1, 1966 R. J. BERT] AUTOMATIC CONTROL MEANS FORRETARDERS 6 Sheets-Sheet 5 Filed Jan. 6, 1954 Pic-3.4:-

ATTORNEYS Nov. 1, 1966 R. J. BERT! 3,283,146

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I) r"r UHU L T.. S- d o O E aw m r' (DO Or- N S. @3595 T L j-o -o o- WElli INVENTOR PfiLAND 8597/ ATTORNEYS 3,283,146 AUTOMATEC CONTRQL MEANSFUR RETARDERS Roland J. Berti, Omaha, Nelm, assignor to Westinghouse AirBrake Company, Swissvale, Pa., a corporation of Pennsylvania Filed Jan.6, 1954, Ser. No. 402,572 Claims. (Cl. 246-182) This invention isconcerned with a speed control system for railway cars and findsparticular application in freight car classification yards. Present dayclassification yards are of the well known gravitational type morecommonly termed hump type and include car retarders for the purpose ofappropriately braking the cars to reduce their speed.

Classification yards of this type include a plurality of individualclassification tracks that are arranged to receive and store the freightcars that are to be classified according to the destination. The carsare pushed over the hump and permitted to coast down an inclined portionof the main entrance track, through the various retarders, and throughthe track switches until they reach the particular classification trackthat corresponds to the ultimate destination of the car.

The principal purpose of the hump is to accelerate the cars, therebygiving the cars sufficient momentum to reach their ultimatedestinations, and also introducing suflicient spacing between successivecars to permit the necessary switching operations to be carried out. Theretraders cooperate in this operation and assist in maintaining thisspacmg.

Most classification yards employ three retarders for this purpose, andaccording to the present invention it is proposed to utilize one or moreof these retarders in a system for controlling the coupling speedbetween successive cars. The term coupling speed is used to describe thecar speed at the instant that the car, while traveling down its selectedclassification track, encounters or engages the stationary cars that arealready stored on that track. If the cars are not retarded sufiiciently,excessive impacts result and frequently cause damage to the cars and thelading, or, on the other hand, if they are retarded too much, excessivespacing between cars on the classification tracks results and thiscauses inefficient utilization of trackage. In addition the excessivespacing frequently causes the immediately successive cars to strike thespaced car at excessive speeds and results in additional impacts thatmay be of an even more damaging character. The damage claims arisingfrom excessive impact of the cars during the classification process isone of the major burdens carried by the railroad industry and thoughmany solutions to this problem have been proposed, lading damage remainsexcessively high. The nub of this lading damage problem is to accuratelycontrol the coupling speed of the cars.

Retarders have been employed in speed control systems for classificationyards previously but until this time it has not been possible toaccurately control the speed of coupling. In these prior art systemsthere have been various attempts made at regulating the speed based onsuch factors as the car weight, the condition and type of bearings, thecondition of the track, and the climatic conditions, but none of thesesystems have properly correlated all of these factors.

It is the principal object of the present invention to provide a controlsystem capable of accurately regulating the coupling speeds of the carsbeing classified. This is accomplished by controlling one of the trackret arders, preferably the last one, in a manner so as to cause a carbeing classified to leave that retarder at a predetermined velocity suchthat the car will arrive at the coupling point 3,283,145 Patented Nov.1, 1966 with an optimum coupling speed. The novel system recognizes thatso-called hard running cars must leave the retarder at a higher speedthan the so-called easy running cars and there is provision made fordetermining the rolling characteristic ofeach car. In regulating theexit speed, it is also necessary to account for the distance the carmust traverse in traveling from the exit of the retarder to the couplingpoint, as well as the gradient of the track over Which the car musttravel in reaching its destination. All of the above enumerated factors,with the exception of the rolling characteristic, are functions of thephysical layout of the particular classification yard and may beempirically determined. These factors associated with the physicallayout of the yard may be conveniently termed the track characteristicsand include, for example, range and gradient for the particular track towhich the car in question is to be shunted. The rolling characteristics,on the other hand, vary for each car and must be determined in the caseof each car. The term rolling characteristic as used herein is definedto include all of the factors which affect the travel of the car otherthan gravity and retarder forces. In positive terms some of the factorsthat aifect the rolling characteristic of a car are its journalfriction, its flange friction, its wheel friction, its weight, and theprevailing wind conditions, and though it is next to impossible todetermine the individual effect of these various factors, the system ofthe present invention determines their composite effect with great ease.

According to the present invention this is done by passing the car overa section of track of known grade, and measuring the resultantacceleration of the car during its travel over the section. The rollingcharacteristic is the difference between the acceleration produced bygravity on this test section and the measured acceleration. Theacceleration factor produced by the test section depends upon its slopegradient and upon the condition of the rails, Having determined therolling characteristic, and knowing the track characteristics of thetrack to be traversed by the car after leaving the retarder, it ispossible to predetermine the exit speed which a car must have whenleaving the retarder. It is an important feature of the presentinvention that though the weight is recognized as one of the factorsafiecting a cars rolling characteristic, it need not be individuallydetermined.

In controlling the operation of the retarder so as to cause the car toleave at a predetermined speed, two fundamentally different systems areavailable. In one, a speed monitoring device applies a braking force asrequired so that the car leaves the retarder at the desired exitvelocity.

In the other system the braking characteristic of the car is determinedin order to apply an appropriate amount of braking effort to reduce thecar speed from the speed at which it is traveling when entering theretarder to the predetermined leaving speed. By braking characteristicis meant the retardation effect that is produced on a given car by theapplication of a known retarder pressure. The braking characteristic ofa car depends upon a number of factors including the weight of the car,the contour shape of the wheel fianges (it being assumed that theretarder being employed is the type that grips the wheel flanges), thefrictional coefficients of the engaged surfaces, etc., but here again itis not necessary to measure the individual effect of these factors butrather the composite effect.

In the preferred form of the present invention, the system fordetermining braking characteristics is combined with the system fordetermining rolling characteristics and a number of possiblecombinations present themselves. Generally speaking, this compositesystem contains two unknown, namely the rolling characteristic and thebraking characteristic, and hence two test sections capable of providingtwo tests are required. There are many ways of running the two tests.The simplest, of course, is to run a first test (test A) that does notinclude any braking forces and thereby enable the single remainingunknown, namely the rolling characteristic to be determined immediately.The means for making this determination may be identical with thepreviously described arrangement. In this form of the invention thesecond test (test B) necessarily must include a braking force applied bya retarder in order to determine its effect upon the car. It is alsopossible to apply a braking force during both test A and test B, theonly proviso being that the braking force be different during each test.

According to the present invention, the test sections are located on thehump incline that leads into the main body of classification tracks.This location is chosen in order to insure that the rollingcharacteristic as determined in the test section remains substantiallyconstant during the travel of the car along the classification track.Certain of the factors making up the rolling characteristic are subjectto wide variation and the accuracy of the system depends on eliminatingsuch variations.

One of these is the effect of the winds which can be of varyingmagnitude and direction, sometimes acting to retard the cars and atother times acting to accelerate them. For this reason it is desirablethat the test section closely simulate the wind conditions prevailing inthe classification yard and although the proposed location on the humpis at a slightly higher elevation and on a steeper gradient than thelocation of the classification track, the windage effect on the car isconsidered to be essentially the same. It is desirable of course, thatthe test section of track, as nearly as possible be parallel to theclassification tracks.

Another highly variable factor is the effect of journal friction whichis dependent not only upon ambient temperature but also upon whether thecars being classified are from a recently arrived train and consequentlyhave warm journals or are from a train that has been standing for sometime in cold Weather. For this reason it is necessary that the test runhe made immediatley previous to the classification run in order that noappreciable change in journal friction can occur and the proposed humplocation adequately meets this condition.

As heretofore explained, the invention compensates for the progressiveshortening of the effective length of the classification tracks thatoccurs as the successive cars being classified are stored on thesetracks and according to the present invention this is accomplishedautomatically.

Other objects and advantages of the invention will be apparent duringthe course of the following description.

A'preferred embodiment of the invention is shown in the accompanyingdrawings in which:

FIGURE 1 is a diagrammatic plan view of the hump and the associatedclassification tracks.

FIGURE 2 is a diagrammatic profile of the hump and an associatedclassification track.

FIGURES 3, 4 and 5 assembled side by side in the order stated constitutea diagram of an electrical circuit whereby the desired control signal isproduced.

FIGURE 6 is a simplified diagram of the circuit of a servo-translatorwhich may be used with the invention.

FIGURE 7 is a simplified diagram of the circuit of a servo-multiplier(or divider).

FIGURE 8 is a simplified diagram of a vacuum tube coupler which may beused with the invention.

FIGURE 9 is a circuit diagram of a modified form of the invention.

In order to best understand that the apparatus of the invention operatesin accordance with the general principles of the invention, as expressedhereinbefore, it is helpful to express these principles mathematicallyand then show that the apparatus conforms to the mathematicalrelationships.

According to the law of conservation of energy the energy of the car maybe stated mathematically as follows:

where the subscripts O and 1 denote respectively the value of thatvariable at an original or reference point and at some other point, and

V=velocity m=mass h=elevation F =net force (a constant) acting on thecar between points 0 and 1 g=acceleration due to gravity D=distancebetween points 0 and 1.

Stated in words, the law of conservation of energy tells us that a bodywhich initially possesses a certain kinetic energy /2mV and a certainpotential energy (mg/z) will, in moving from one point to another,undergo a change in total energy /zmV +mgh) which is equal to the amountof work done on or by that body while moving between those points. Ifthe forces acting on the body during this motion are constant, the workis equal to the product of the force multiplied by the distance betweenthe points (FD).

Using the subscript e to designate the exit of the main retarder and fto designate a point in the classification yard at which a car beingclassified will couple with a standing car and using the English systemof weights and measures, the following equation may be derived from theequation given above but relating to the car speeds at the points e andf:

Substituting h for (h -h and 32.2 ft./sec. for g, then solving the aboveequation for V the following equation This approximation holds true ifthe gradient is slight, as it is in a classification yard. Making thissubstitution in Equation 1, the following may be derived.

The same equations may be set up for motion of the car duringapplication of the test brake forces while the car is on the hump.

It will be apparent that the net force, E in Equations 1 and 1a, actingon the car during travel through the yard is the resultant of the forcesdue to friction, windage, condition of the track and the like. The netforce acting on the car at any time during descent along the humpincludes these same retarding forces plus the test braking force that isacting.

According to the preferred form of the invention, by measuring thevelocity changes which occur as a result of the different forces actingduring travel down the hump it is possible to compute the final brakngforce necessary to produce an exit velocity at the bottom of the humpsuch that the car will reach its destination at a proper velocity.

Referring first to FIGURE 1, it will be seen that eight pairs ofphotoelectric cell relays and associated light sources are employed.These are indicated by reference numerals 111, 12, 13, 14, 15, 16, 17and 18. During travel between the photoelectric cells 11 and 13, a firsttest brake force F,, is effective, and during travel from photoelectriccell 14 to photoelectric cell 16 a different. test brake force F iseffective.

The photoelectric relays ll, 12, 13, 14, and 16 are arranged along thetrack with the light sources on one side of the track and the lightsensitive relays on the 0pposite side, so arranged that as long as nocar is occupying the track between, the light sources project into theirrespective photoelectric cells thus energizing the relays. These lightsources and relays are arranged in such a manner so as to provideclearance for any railway vehicle which may occupy the track, and alsoso that the light beams will be interrupted, and remain interrupted forthe entire length of travel of a car or group of cars. A preferredlocation is to have the light beams normal to the track centerline andat a height so that the beam will be interrupted by the car couplers andconnecting underframe. The light source should preferably be lower thanthe photoelectric relay so that the light beam crosses the track at anangle with the horizontal, thus assuring beam interruption for all typesof cars including depressed underframe fiat cars.

The spacing of the photoelectric relays 11 to 16 is dependent upon themechanical and electrical constants of the system and in practice may bea great number of values, depending upon such factors as the speedresponse of the relays, the speed response of the retarder, the valuesgiven to the various circuit components, etc.

It will be understood that while photoelectric relays are used in theillustrated embodiment, these components could also be car actuatedtreadles, or similar devices.

It has been stated that the test braking forces F and P are not equal.In other words, E is some multiple of F,,.

The symbol n will be used to identify this multiple. Statedmathematically, F =nF Since the forces F and F are, by definition,unequal, n is some number other than 1. Using the mathematical statementof the law of conservation of energy as set out above, the motionbetween the points a and b and c and a may be stated according to thefollowing equations wherein F =net retarding force other than the testbraking force:

(2a) Fangs-v1.

Since 100 11/8 is approximately equal to the percent gradient of thetrack between the points a and b, and using the symbol k to representpercent gradient, the following equation may be derived:

A corresponding formula for motion from c to d may be derived in thesame manner from Equation 3.

2. 2 b+ r c d m 25' Since by definition F nF nF may be substituted forE, in Equation 3a to obtain the following equation:

Equations 2b and 3b are a pair of simultaneous equations having twounknowns F and F To eliminate F and solve for P we subtract Equation 2bfrom Equation 3b to obtain the following equation:

2S (nl) The solution of simultaneous Equations 2b and 3b for the otherunknown P is acomplished by multiplying Equation 212 by n andsubtracting Equ-a-tion 3b therefrom to obtain:

2S(nl) If n=1, i.e., if F F the solutions of 4a and 50 for F /m and F /mrespectively are indeterminate. Hence n may not equal 1 if a solution isto be obtained. As a practical matter n could equal zero. In this case,we would obtain from Equations 4a and 5c respectively:

Theoretically n could have a value less than zero in which case theforce P instead of being a braking force would be an assisting force.Practically considered the value of n will usually be positive becauseof the ease of applying a braking force as contrasted to the applicationof an assisting force.

If two test forces are used a value of n 1 is preferred, because thebraking bars of track side retarders are ordinar ily pneumaticallyactuated and air is conserved if the braking force is progressivelyincreased whereby it is unnecessary to vent any air from the retarderactuating means.

It will be assumed for the purposes of convenience in disclosing theillustrated embodiment of the invention that 11 2. Substituting thisvalue of n, the following formulae are derived from Equations 4a and 5crespectively:

T 2 S +0.322K

Motion of the car from the photoelectric cell relay 16 to the exit ofthe main retarder may, in accordance with the mathematical statement ofthe law of conservation of energy, be stated as follows:

The term F represents the main braking force while h and D are indicatedby legend on FIGURE 2. In Formula 6 it is assumed that the differencebetween the velocities :at point d and the photoelectric cell relay 16can be ignored without introducing a significant error. The followingformula can be derived from Equation 6 in a manner generally analogousto the derivation of 2b from Equation 2.

(6a) ELM m 2D +0.322lc H Multiplying the right hand side of 6a by F /m F/m 7 and cancelling we obtain: g

2 2 (7) +0.322lc- F =F F m Since the force F is the total applied toboth car trucks, and the test braking forces are applied to one truckonly, the actual force to produce this braking force is half F This.force will be designated F w J: F L51 2D +0.322k m in which F representsbraking force, P represents the pressure then acting, A is the area ofthe retarder motor means, and p equals the coefiicient of friction.

E by definition, is the main retarding force acting on the car betweenthe points d and e and therefore may be stated mathematically asfollows:

in which P represents the retarder pressure acting on the car as ittravels between the points d and e.

Similarly F,,, the test braking force, may be mathematically stated as:

F =P Ap wherein P represents the retarder pressure acting on the car asit travels between points a and b.

By substituting the above terms for E and F in Equation 7a, thefollowing equation may be derived:

(7b) V VJ F The factor A r, since it would appear on both sides ofEquation 717, has been cancelled out from both sides.

Referring now to FIGURE 3, reference numerals 21, 22, 23 and 24 indicategenerally resistoncapacitor units which are connected in parallel with abattery 25. Resistor-capacitor until 21 comprises a resistance 26 and acapacitor or condenser 27 connected in series across the "batteryterminals. Flow through the resistance 26 and capacitor 27 is controlledby relay switch contacts 11A and 12A. The relay switch contacts havebeen numbered according to the convention in which the numeral indicatesthe photoelectric cell, see FIGURES 1 and 2, and the relay controlledthereby and the reference letter indicates the contact actuated by therelay. These switches are shown in the position assumed when theassociated relay is energized, i.e. when no car is on the hump. Theopposite sides of the condenser 27 are connected to a high inputimpedance type vacuum tube coupler 28, and with this arrangementsubstantially no dissipation of condenser voltage occurs through thecoupler 28. Deenergization of relay 11 closes contact 11A whereby acharge is accumulated on the condenser 27. This charging is terminatedby the opening .of contact 12A upon the denergization of relay 12. Anormally open contact 18A is connected as a shunt between the condenseroutput leads to the vacuum tube coupler 28 and is effective when closedto dissipate the charge on the condenser 27, as will be more fullyexplained. The unit 22 is similar to Q unit 21 but charging flow to thecondenser is controlled by normally open relay contact and terminated bythe opening of normally closed contact 13A. The units 23 and 24 areidentical to units 21 and 22. Their serial energization is controlled bythe relays associated with the photoelectric cells 14, 15, and 16.

The vacuum tube couplers 28, 29, 3t and 31 are identical and theirconstruction will be clear from the diagrammatic showing of coupler 28in FIGURE 8. It comprises a conventional vacuum triode 32 having a highinput impedance obtained by biasing the grid so that it is negative atall times and using a large grid leak resistor 33 in relation to thecapacitor 27. In this way only a small part of the capacitor output islost during the time the car moves through the retarder. The platepotential in turn is made high enough so that it will be in theconducting range even though the grid is negatively biased. The tubeplate and grid potentials are selected so that the plate current flowingthrough the plate resistor 34 is linearly proportional to the capacitorvoltage. A selected portion of this output is impressed on a vibratingreed DC. to AC. converter and hence supplied to an output transformer.

The secondary of the output transformer is electrically connected to aservo-translator 35. Similar servo-translators 36, 3 7, and 38 arerespectively connected to couplers 29, 30, and 31. Theseservo-translators are identical and only a description of translator 35will be made. See FIGURE 6. The input from the coupler 28 is connectedin series to a voltage amplifier 39 and to a variable potentiometer 41.Amplifier output is supplied to a field winding of a reversible twophase servo-motor 42 which is connected to drive the potentiometer 41and an output potentiometer 43. The output from potentiometer 43 is inturn supplied to the primary winding 44 of transformer 45 (see FIGURE3). Potentiometer 41 is in effect a follow-up device to denergize theservo-motor 42 when the output setting reaches a value corresponding tothe input from the coupler 28. The winding of potentiometer 43 is suchthat the output is inversely proportional to the square of the input tothe translator.

Similar transformers '46, 47 and 48 are connected to receive the outputof translators 36, 3'7 and 38 respectively. The charge on capacitor 27is linearly related to the time it takes the car to travel fromphotoelectric cell 11 to cell 12. A signal which is inverselyproportional to the square of this charge is proportional to the squareof the average velocity of the car while travelling from phot-o-electriccell 11 to photo-electric cell 12. Hence the primary windings oftransformers 45, 4s, 47 and 48 are energized by voltages which arerespectively proportional IO V32, V132, V02 and Va A linearpotentiometer 49 is connected across an independent .A.C. source. Thesetting of this potentiometer is selected so that it gives an outputsignal proportional to the percent gradient of the hump which is aconstant. This output is connected to the primary winding of transformer51 and produces a corresponding signal in each of its secondarywindings.

The network including leads 52 and 53 and selected secondary windings(as shown in FIGURE 3) produces a voltage signal E=V +V +V V which isproportional to F /m (Equation 40) since S is a constant. The term F /mis a measure of the braking effectiveness of the retarder for the car inquestion, and hence the control energy represented by the signal E isproportional to the braking characteristic of the retarder for the car.The network including leads 54 and 55 and the illustrated transformersecondaries produce a voltage signal of the car in question, and hencethe control energy represented by the signal E2 is roportional to therolling characteristic of the car. Connected across leads 52 and 53 is avoltmeter 56 which may be calibrated to indicate car Weight. Thisindication of car weight is approximate. Similarly a voltmeter 57 isconnected across leads 54 and 55 and is calibrated to indicate the netretarding force other than braking forces which is acting on the car.

Two signals corresponding to classification track conditions must beproduced and this is accomplished as shown in FIGU RES 4 and of thedrawings. Associated with the signal transmitting line from eachclassification track is a selector switch means indicated generally byreference numerals 61, 62, 63, 64, 65 and 66. These switch means areidentical and only means 61 will be described in detail. Means 61includes a normally open main selector switch 67 which may beautomatically controlled or manually controlled by the humpmaster. Whenswitch 67 is closed the associated relay 68 is energized wherebyassociated contacts 68B, 68C, 68D and 68E are closed and contact 68A isopened. Opening of contact 68A prevents energization of relays 69, 70,72, 73 and 74. It will be noted that each selector switch means issubservient to energization of the relays ahead of it in the series, butdominates those subsequent to it in the series.

Closure of contacts 68B, 68C, 68D and 68B connects signal leads 75, 76,77 and 78 to the corresponding stepping relay 79. The selector switchmeans each includes a stepping relay. These relays are indicated byreference numerals 79, 81, 82, 83, 84 and 85.

Stepping relay 35 is identical with the others and is shown in diagramin FIGURE 5. Associated with each classification track at its entranceis a light source and photoelectric cell relay. These are indicated at86, 87, 88, 89, 91 and 92 in FIGURE 1. Relay 92 controls contact 92A ofstepping relay 85. Stepping relay 85 includes two potentiometers 93 and94. Potentiometer 93 has a winding calibrated so that its output signalis an indication of the distance from the exit of the retarder to thenearest car on the track. Potentioineter 94 is wound so that its signalis an indication of the average gradient (K) between the correspondingpoint on the classification track and the exit of the retarder. Theaverage gradient is proportional to the change in potential energy whichthe car undergoes in traveling over the portion of track to which theaverage gradient corresponds. The potentiometers 93 and 94 are drivenfrom single shaft (indicated by a dotted line). This shaft is driven byeither of two ratchet wheels and relay combinations 95 and 96. Assembly96 is actuated by closure of contact 92A. It acts to adjust the settingsof potentiometers 93 and 94 as required by the admission of a single carto the corresponding classification track. This adjustment of 93 and 94is determined by use of an average car length. An unusual run of longcars or short cars will require that the setting of the potentiometersbe adjusted. If a run of long cars occurs the adjustment is made bymanually closing contact 99 against contact 98. If a run of short carsoccurs contact 99 is closed against contact 97 whereby relay assembly 95is energized to cause a reverse adjustment of potentiometers 93 and 94.During readjustment, a pulsating current is supplied to relay assemblies95 and 96, so that the humpmaster may count the number of pulsations andknowing the desired correction and the observed average length of thecars, he may establish the proper settings.

Although the same effect could be had by repeatedly opening and closingswitch 92, automatic means such as the cam operated switch 101 ispreferred. A single switch 101 can be used to control the readjustmentof all the stepping relays 79, 81, 82, 33, 84 and 85.

Potentiometer 93 is connected across leads 75 and 76 and potentiometer94 is connected across leads 77 and 78. A voltmeter 102 may be connectedacross leads 75 and 76. This voltmeter can be used as an indication ofthe range setting, i.e., the indication of the distance from retarder tothe nearest car on the corresponding classification track.

The indicated range signal is supplied to the primary winding oftransformer 163, and the indicated average gradient signal is suppliedto transformer 1%. The secondary winding of transformer 103 is designedto produce a signal equal to twice the range (2D and is connected tosupply this signal to the input connection 105 of the servo-multiplier106. Input connection 107 receives a signal from transformer andtransformer 104 equal to F,/m-K.

The output from multiplier 106 equals 2D (F /m-K). An adjustablepotentiometer 108 is connected to the output of multiplier 106. Thewinding of potentiometer 108 is selected to produce a signalproportional to V Servo-translator'109 receives an input equal to i.e. Vaccording to Equation 10. Servo-translator 109 is similar to toservo-translator 36, but is arranged to produce a modified signal equalto the square root of the input. The square root of the input is equalto V (according to Equation 10). This output signal is supplied to oneof the coils of differential relay 111. The other coil of relay 111 isconnected to the radar speed indicator 112. The purpose of this relay111 will be explained.

The signal V is also supplied to a transformer 113, the secondarywinding of which produces a signal V 2D. The secondary windings oftransformers 113, 110, 48 and 51 are connected in series and supply tothe input 114 of the servodivider 115 a signal equal to This output issupplied to input 117 of servo-multiplier 118. .A signal proportional toP,,,/ 2 is supplied to input 119. The output from servo-multiplier isapplied to a primary winding of transformer 121.

The signal P /Z is produced as follows: a fixed potentiometer 122 isprovided with three taps 123, 124 and 125. Potentiometer 12-2 is woundso as to produce a voltage between the points 126 and 123 proportionalto P,, /2, between points 126 and 124 a signal proportional to P andbetween 126 and 125 a signal proportional to 2P,,.

A lead extends from 126 to parallel connected contacts 16C and 17A toinput connection 119 and back to tap 123. Contact is controlled by therelay associated with photoelectric cell 16. Contact 17A is controlledby the relay associated with photoelectric cell 17. There may be morethan one relay such as 17 and these relays act to maintain at least oneof the parallel connected contacts closed at all times during a carsdescent through the main retarder section.

Contacts 16D and 17B open the circuit to the second primary winding oftransformer 121 whenever either relay 16 or 17 is deenergized, as willbe the case when a car is in the main retarder. Contacts 13C and 13D actduring the cars travel while subject to either of the two test brakingforces in a manner such that the input to this second primary winding iseither P or Q P The output of servo-multiplier 118 is a signalproportional the solution of Equation 7b, i.e., the desired brakingpressure.

The secondary winding of transformer 121 is connected in a seriescircuit which includes relay contacts 18E.

and front contact 111A, error potentiometer 130 and amplifier 127. Theamplifier output is connected to a field winding of motor 12-8 whichoperates three-way valve 129. Valve 129 controls the supply anddischarge of pressure fluid to and from the operating motors of theretarder. The motor pressure is effective through bellows motor 140 toadjust potentiometer 130.

When the radar speedmeter 112 indicates the speed of the car after thetest braking forces have been applied is less than the desired exitvelocity from the hump, the circuit through the front contact 111A ofthe differential relay 111 is opened and a second circuit is establishedto the reta'rder-controlling motor through the back contact 111B whichis now closed. This causes the retarder operating motors to be vented.The radar speed indicator has a range such that it measures the speed ofcar only during the interval after it has left the test braking sectionof the retarder and prior to its exit from the retarder. Contact 18B isclosed against its front contact when the photo-electric cell 18 isenergized, and closes against its back contact to vent the retardermotors in the same manner that the retarder motor is vented by operationof the differential re'lay 111. Contact 18E closes its front contactwhen the photoelectric cell relay 1% is again energized which occurswhen the rear end of the car passes that relay. At this same timecontacts 18A, 18B, 18C, and 18D are closed to dissipate the charge onthe condensers of resistor-capacitor combinations 21, 22, 23 and 24.

A simplified diagram of servo-multiplier 106 and 118 and servo-divider115 is shown in FIGURE 7. These units comprise three input connections131, 132, and 133. Input connection 131 is connected in series with avoltage amplifier 134 and error potentiometer 135. Amplifier output issupplied to motor 136 which controls the setting of potentiometer 135and an output potentiometer 137. When used as a multiplier input 132 isconnected to a suitable independent A.C. source, and inputs 131 and 133are connected to receive the multiplier signal and the mu'ltiplicandsignal respectively. The output from potentiometer 137 to connection 138is a signal equal to their product. When used as a divider the dividendsignal is connected to 131 and the divisor signal is connected to 132,and the independent A.C. source is connected at 133.

It will be seen that apparatus has been provided whereby equation 7b issolved electrically to produce a voltage signal proportional to thebraking force required to slow the car to the proper speed when itleaves the hump, so that it will reach its destination and reach it witha desired final velocity.

As has been said only one test braking force need be applied. SeeEquations 4b and 5d. However the use of two is preferred, because inthis Way a braking force is applied to the car at all times during itsdescent along the hump, whereby the full length of the hump is used tocontrol car speed.

A second variation is also possible. Having solved for the desired exitvelocity V a standard main braking force could be employed and itsduration determined by the radar speed indicator, for example, by usinga difierential relay such as 111 connected to vent the retarder acuatingmotors when the car speed was reduced to the desired V,,. This wouldresult in uneven wear of the braking bars and also the heavy brakingforce might cause light cars to be derailed. However, this cincuit isattractive because of its simplicity and further, because it eliminatesthe necessity for using a test braking force.

The circuit whereby this embodiment may be used is diagr'amed in FIG. 9.It includes the servo-translator 109 with its input connected to theoutputs of servo-multiplier 106 and of potentiometer 108 connected inseries as in the preferred embodiment. The multiplier 106 has its input105 connected to the secondary winding of transformer 103 which isenergized to produce a signal pro- 12 portional to ZD The inputconnection 107 is connected to the secondary winding of transformers104, 4-7, 48 and 51 arranged in series to produce a signal The term.322K is fed in through transformer 104 as a voltage signal and it isproportional to the change in poential energy which the car undergoesafter leaving the retarder. The balance of the signal fed to the inputconnection 107 appears as a discrete signal comprising the algebraic sumof the potentials in secondary windings of transformers 47, 48 and 51and is a signal proportional to the rolling characteristic of the car.The output from servo-translator 109 is connected to one winding of thedifferential relay 111. The other Winding of relay 111 is connected tothe radar speedrneter 112. The output from servo-translator 109 is Thisformula is derived by substituting in Equation 1a the value of F /mderived from Equation 5d. So long as the signal V is greater than thesignal from the speedrneter 112, contact 141 is open, whereby thesolenoid of valve 142 is de-energized which admits pressure fluid to theactuating motors of the retarder to establish therein a predeterminedconstant pressure. When the signal V is equal to or less than the signalfrom the speedmete-r 112, the solenoid valve 142 is energized, therebycausing the retarder motor to be vented.

While a preferred embodiment and one modification of the invention havebeen described in detail, it will be understood that there are variousequivalent arrangements which Will occur to those who are skilled in theart. The invention is not limited to the use of a particular type ofcomputer or to a particular type of means for determining the carsvelocity. The underlying principle is the fact that it is possible todetermine the appropriate car speed at the exit of the retarder in orderto produce the optimum coupling speed and also to determine the optimumbraking force to be applied in order to produce this exit speed bymeasuring the velocity changes which occur during descent by the caralong an initial portion of the hump and by measuring the car speed atthe entrance to the retarder.

What is claimed is:

1. In combination, a classification yard including a retarder having anexit leading into a track section of known track characteristics, saidtrack section extending from the exit of said retarder to a destinationin the yard at which a car is to couple at a desired velocity, means forgenerating control energy corresponding to the rolling characteristic ofsaid car, means for generating control energy corresponding to the trackcharacteristics of the track section to be transversed by said car,computing means for combining all of said control energies to produce aresultant control energy corresponding to the speed at which the carmust leave the retarder to arrive at the destination at the desiredvelocity, said computing means including means representative of saiddesired coupling velocity and cooperating with said control energies toproduce said resultant control energy, and means for generating acontrol energy representative of the braking characteristic on said carby said retarder, and means jointly responsive to said resultant controlenergy and to the braking characteristic control energy for controllingthe retarder.

2.. In combination with a classification yard having a hump, a pluralityof classification tracks arranged in parallel relation with each otherand each being selectively connectable to the lower end of the hump, anda car retarder disposed along a portion of the length of said hump, acar-controlling system for regulating the velocity of a car as itreaches its destination on a selected classification track, said systemcomprising means for generating a signal proportional to the combinedretarding forces acting on said car as it rolls freely down the hump,means for generating a signal proportional to the length of trackbetween the lower end of the retarder and said destination, means forproducing a signal proportional to the change in elevation which a carexperiences in moving from the lower end of the retarder to saiddestination, means for producing a signal which is a function of thedesired velocity of the car as it reaches said destination, computingmeans for combining all of said signals to produce a resultant signalcorresponding to the velocity the car must have in leaving the retarderto achieve said desired velocity, means for producing a signalproportional to the braking characteristic of said retarder for the car,actuating means for energizing the retarder, and means for regulatingsaid retarder actuating means in accordance with the resultant signaland the braking characteristic signal 3. In combination with aclassification yard having a hump, a plurality of classification tracksarranged in parallel relation with each other and each being selectivelyconnectable to the lower end of the hump, and a main car retarderdisposed along a portion of the length of said hump, a car-controllingsystem for regulating the velocity of a car as it reaches itsdestination on a selected classification track, said system comprisingtwo sections of test track located on the hump above the entrance to themain retarder, a test retarder associated with each test section, meansfor actuating each test retarder a known but different amount, meansoperative as a car traverses said test sections for producing a firstsignal proportional to the combined retarding forces, other than brakingforces, acting on the car, and a second signal proportional to thebraking characteristic of said test retarders for the car, means forgenerating a third signal proportional to the length of track betweenthe exit of the main retarder and the cars destination, means forgenerating a fourth signal proportional to the average gradient of thetrack between the retarder exit and said destination, means forproducing a fifth signal which is a function of the desired velocity ofthe car as it reaches said destination, means for producing a sixthsignal corresponding to the sum of the products of said first and thirdsignals and said third and fourth signals, means for producing a firstresultant signal corresponding to the algebraic sum of said fifth andsixth signals, means for producing a seventh signal which is a functionof the velocity at the entrance of the main retarder, means forproducing an eighth signal proportional to the gradient of the mainretarder, computing means for algebraically adding said first, firstresultant, seventh and eighth signals and for dividing the sum by saidsecond signal to produce a final resultant signal corresponding to thequotient, and control means for actuating said main retarder inaccordance with the final resultant signal.

4. In combination, a hump-type classification yard having a section oftrack located forwardly of the exit of a car retarder and a tracksection extending rearwardly from the exit of said retarder to adestination in said yard at which a car is to couple at a desiredvelocity, means for measuring the resultant acceleration of the car asit rolls freely over said forward section of track and for producingcontrol energy corresponding to the difference between the measuredacceleration and the acceleration due to the velocity-changing effect ofsaid forward section of track, means for generating control energycorresponding to the range of the rearward track section to be traversedby the car, computing means combining all of said control energies toproduce a resultant control energy corresponding to the speed at whichthe car must leave the retarder to arrive at the destination at thedesired velocity, means for applying the retarder to the car as it rollsover said forward section of track for measuring the velocitychangingeffect of the retarder for the particular car and producing a brakingcontrol energy corresponding thereto,

and means for combining said resultant control energy and said brakingcontrol energy for controlling the retarder.

5. In combination with a classification yard having a hump, a pluralityof classification tracks arranged in parallel relation with each otherand each being selectively connectable to the lower end of the hump, anda car retarder means disposed along a portion of the length of saidhump, a car-oontrolling system for regulating the velocity of a car asit reaches its destination on a selected classification track, saidsystem comprising means for generating a signal proportional to the com-:bined retarding forces acting on said car as it rolls down the hump,means for automatically generating a signal proportional to the lengthof track between the exit end of said retarder means and saiddestination, means for producing a signal proportional to the change inelevation which a car experiences in moving from the exit end of saidretarder means to said destination, means for providing a signal whichis a function of the desired velocity of the car at its destination,computing means for combining all of said signals to produce a resultantsignal which is a function of the velocity the car must have leavingsaid retarder means to achieve said desired velocity, said car retardermeans including a test retarder section for generating a signalproportional to the braking characteristic of said oar, means forproducing a signal proportional to the velocity of the car at theentrance to said retarder means; means for combining said resultantsignal, said braking characteristic signal, and said entrance velocitysignal and operable in accordance with the combined signal for actuatingsaid retarder means so that the velocity of the car traversing thatretarder means is varied at a constant rate from the velocityrepresented by said entrance velocity signal to the exit velocityrepresented by said resultant signal.

6. Apparatus for controlling the speed of a. cut of cars leaving a carretarder located at the entrance end of a stretch of track of knowncharacteristics in order to arrive at the end of said stretch at apredetermined terminal velocity, comprising, in combination, means formeasuring the rolling characteristic of said cut, means forautomatically measuring the length of said stretch, means for generatinga signal in accordance with said rolling characteristic and said lengthproportional to the velocity at which said cut should leave saidretarder to arrive at the end of said stretch at said predeterminedvelocity, means for measuring the speed of said cut in said retarder andproducing a signal in accordance therewith, means for measuring thebraking characterstic on said cut by said retarder, and means jointlycontrolled by the difference between said measured speed signal and saiddesired speed signal and by said measured braking characteristic forcontrolling said retarder at a constant rate to reduce the leaving speedof said cut from said retarder to said desired value using substantiallythe entire length of said retarder.

7. Speed control means, comprising, in combination, a car retarderlocated intermediate a first and a second stretch of track, meansassociated with said retarder for measuring the rolling characteristicsof each car, means automatically adjustable in accordance with thevarying length of said second stretch of track, means automaticallyadjustable in accordance with the varying average grade of said secondstretch of track, means for measuring the speed of each car in saidretarder, means associated with said retarder for measuring the brakingcharacteristic on each car by said retarder and means jointly controlledby both said measuring means and by both said adjustable means foradjusting the braking force exerted on each car by said retarder to aconstant force maintained through substantially the entire length ofsaid retarder so that each car approaches the exit end of said secondstretch at a desired speed.

8. In a car retarder control system, a controllable car retarder in astretch of railway track having an operating mechanism operable toposition the car retarder for selected degrees of retardation, a testarea at the entrance end of said car retarder for providing a fixeddegree of retardation, speed responsive means for detecting the effectof the fixed retardation in said test area upon the speed of a car, andcircuit means for selecting the degree of retardation for saidcontrollable ca-r retarder in accordance with the effect of said fixedretardation in said test area upon the speed of the car as detected bysaid speed responsive means.

9. In a car retarder control system, the combination of, a car retardermeans having a section with a fixed degree of retardation and anothersection with a controllable degree of retardation, speed responsivemeans responsive to a car moving through said fixed retardation sectionfor detecting the effect of the retardation upon the speed of said car,and control means controlled by said speed responsive means forcontrolling the degree of retardation in said controllable section inaccordance 1 With the effect of said fixed retardation upon the speed ofsaid car.

10. In combination with a classification yard having a hump, a pluralityof classification tracks arranged in parallel relation with each otherand each being selectively connectable to the lower end of the hump, anda car retarder disposed along a portion of the length of said hump, acar-controlling system for regulating the velocity of a car as itreaches its destination on a selected classification track, said systemcomprising means for generating a first signal proportional to thecombined retarding forces acting on said car as it rolls down the hump,means for automatically generating a second signal proportional to thelength of track between the retarder exit and said destination, meansfor automatically producing a third signal proportional to the averagegradient which a car encounters in moving from the retarder exit to saiddestination, means for providing a fourth signal which is a function ofthe desired velocity of the car at its destination, commuting means formultiplying the first and second signals and algebraically adding theproduct With the third and fourth signals to produce a first resultantsignal corresponding to the sum, means for producing a second resultantsignal proportional to the square root of said first resultant signal,means for generating a fifth signal proportional to the brakingcharacteristic on said car by said retarder, and control meansresponsive to said first and second resultant signals and to said fifthsignal for controlling the retarder to reduce the velocity of said carat a constant rate throughout substantially the entire length of saidretarder to obtain said desired velocity at the destination of said car.

References Cited by the Examiner UNITED STATES PATENTS 1,626,920 5/1927Coleman 10426.1 X 1,766,539 6/1930 Prescott 10426.1 X 1,958,294 5/1934Bone et al. 10426.1 X 2,361,466 10/1944 Fitzsim-mons 10426.1 2,477,5678/ 1949 Barker. 2,549,146 4/1951 Van Horn 24629 X 2,629,865 2/1953Barker. 2,679,809 6/1954 Beltman et al. 10426.1

FOREIGN PATENTS 921,845 1/1947 France. 601,508 8/ 1934 Germany.

OTHER REFERENCES A thesis prepared by Wilhelm Koth and titled DieLaufziels-Tenerung in der Ablaufdynamik, Germany, 151 pages.

ARTHUR L. LA POINT, Primary Examiner.

SIMON SAPERSTEIN, LEO QUACKENBUSH,

Examiners.

J. S. SI-IANK, L. J. LEONNIG, S. T. KRAWCZEWICZ,

Assistant Examiners.

1. IN COMBINATION, A CLASSIFICATION YARD INCLUDING A RETARDER HAVING ANEXIT LEADING INTO A TRACK SECTION OF KNOW TRACK CHARACTERISTICS, SAIDTRACK SECTION EXTENDING FROM THE EXIT OF SAID RETARDER TO A DESTINATIONIN THE YARD AT WHICH A CAR IS TO COUPLE AT A DESIRED VELOCITY, MEANS FORGENERATING CONTROL ENERGY CORRESPONDING TO THE ROLLING CHARACTERISTIC OFSAID CAR, MEANS FOR GENERATING CONTROL ENERGY CORRESPONDING TO THE TRACKCHARACTERISTICS OF THE TRACK SECTION TO BE TRANSVERSED BY SAID CAR,COMPUTING MEANS FOR COMBINING ALL OF SAID CONTROL ENERGIES TO PRODUCE ARESULTANT CONTROL ENERGY CORRESPONDING TO THE SPEED AT WHICH THE CARMUST LEAVE THE RETARDER TO ARRIVE AT THE DESTINATION AT THE DESIREDVELOCITY, SAID COMPUTING MEANS INCLUDING MEANS REPRESENTATIVE OF SAIDDESIRED COUPLING VELOCITY AND COOPERATING WITH SAID CONTROL ENERGIES TOPRODUCE SAID RESULTANT CONTROL ENERGY, AND MEANS FOR GENERATING ACONTROL ENERGY REPRESENTATIVE OF THE BRAKING CHARACTERISTIC ON SAID CARBY SAID RETARDER, AND MEANS JOINTLY RESPONSIVE TO SAID RESULTANT CONTROLENERGY AND TO THE BRAKING CHARACTERISTIC CONTROL ENERGY FOR CONTROLLINGTHE RETARDER.
 9. IN A CAR RETARDER CONTROL SYSTEM, THE COMBINATION OF, ACAR RETARDER MEANS HAVING A SECTION WITH A FIXED DEGREE OF RETARDATIONAND ANOTHER SECTION WITH A CONTROLLABLE DEGREE OF RETARDATION, SPEEDRESPONSIVE MEANS RESPONSIVE TO A CAR MOVING THROUGH SAID FIXEDRETARDATION SECTION FOR DETECTING THE EFFECT OF THE RETARDATION UPON THESPEED OF SAID CAR, AND CONTROL MEANS CONTROLLED BY SAID SPEED RESPONSIVEMEANS FOR CONTROLLING THE DEGREE OF RETARDATION IN SAID CONTROLLABLESECTION IN ACCORDANCE WITH THE EFFECT OF SAID FIXED RETARDATION UPON THESPEED OF SAID CAR.